It might seem odd to view the vileness that the Labour Party has disclosed over these last few days as an opportunity. But I'm tempted to believe that Ken Livingstone has done the Jews a service - after years of dodging and weaving, he has finally laid his cards on the table.

He doesn't know it, of course, and never will. To understand one's actions re-quires self-knowledge, and to understand their effect on others requires imagination, and Mr Livingstone is a stranger to both. But he has, once and for all, bust the big lie that you can be an enemy of Zionism and not an enemy of Jews.

I choose my words carefully. An enemy of Zionism. Finding fault with Israel is something else. Who doesn't find fault with Israel? Jews are themselves born fault-finders. We find fault with everything. We almost mean it as a compliment when we do. And don't we even, on occasions, break bread with those who piously call themselves "critics" of Israel, as though they deal in fine discrimination and measured judgment, while the words they speak are wild and whirling? We let them have their say. Perhaps they mean well.

It is important to make the distinction. To inveigh against the policies of successive Israeli administrations is one thing, to inveigh against Zionism - at times the means, for many the only means, of Jewish survival - is another. And now would seem to be our opportunity to insist on that difference with clarity and vigour.

Jeremy Corbyn - the good cop to Mr Livingstone's bad cop (though you wouldn't want to be apprehended by either of them) - will not get far with his attempt to root out antisemitism from his party until he accepts that he has first to get rid of its indurated anti-Zionism, and that is all but impossible for a socialist of his complexion in whose philosophy the heinousness of Israel is inscribed like letters running through a stick of rock.

Back, back to the Soviet show trials it all goes, and further back still to suspicion of Israel as a colonial entity acting at the behest of the imperialist powers.

Socialist Jews will be writing their letters to this paper now, reminding us that anti-Zionism has an honourable history, not least among Jews. But that history can be called honourable only in the sense that naivety can be called honourable - a sincere conviction clung to in the face of knowledge of the world.

Only witness Stefan Zweig's early mistrust of Zionism, and the faith he put instead in a sort of altruistic universalism, and then consider his lonely suicide in a far-flung corner of the Americas, after years, in his own final words, "of wandering homeless". His belief in man's essential goodness was shattered, the universalist dream, against which he judged Zionism, exposed as childish optimism. Maybe there was an alternative to Zionism for Jews when once-friendly countries turned hostile and other nations closed their borders, but no one found it.

I am not advocating militancy. A strident pro-Zionism, proclaiming all the fine deeds Israel has performed and turning a blind eye to the ill, not only provokes antagonism, it is inhumane in itself.

But there are intellectual battles to be fought and today, with Labour's bad faith laid bare, Jews should seize the opportunity to fight them. Let's refute with all our powers the canard that we cry "antisemitism!" only to deflect attention from criticism of Israel. No. Criticism we accept. We cry antisemitism only when antisemitism is what we see, and we are seeing it now.

Let us, without dismissing the concerns of those who dislike what Israel has become or is in danger of becoming, insist on this: Zionism is not and never was an ideology of oppression; Zionism came into being as an expression of Jewish fear and aspiration, a longing for renewal and self-determination occasioned by waves of violence against Jews all over Europe and made increasingly urgent as those fears were given a terrible materiality by the Nazis.

Whoever minimises the threat Jews faced 100 years ago, 50 years ago, and still face today, flirts with the discourse of antisemitism. Whoever accuses Jews of making capital out of adversity paves the way for antisemitism. And whoever describes Zionism as the imposition of Jewish exclusivism and supremacy is an antisemite.

As for people who insist that I say these things only in order to stifle "legitimate criticism" of Israel - as though "legitimate" means saying anything one wants to say - they might not be antisemites yet but they are three quarters of the way there.

Enough. Send those who think Zionism was a con trick on the Palestinians to watch the film Son of Saul, and ask them if the mountains of grey ash to which Jews were reduced did not cry out then and do not cry out still for a place of Jewish refuge.

Son of Saul depicts hell in a way art has never depicted it before. It is not an argument to inflict hell on anyone else. The desperate must acknowledge the desperation of others. But the cruel contigencies of Israeli-Palestinian politics must not be allowed to alter what was hoped for and intended in the past. We cannot read history backwards.

Boycotters do not have a monopoly on compassion. We too cannot bear what we see on our television screens or read in our papers. So let's speak the language of that compassion while insisting that it is possible to feel conflicting emotions simultaneously.

It's a tragedy that two warring peoples, each deserving of a homeland and a life, cannot reach a peaceful accord. We need to demonstrate our historic capacity to feel and think at the same time. The fact that Mr Livingstone and his cheer-squad won't, and many more members of the Labour Party can't, is all the more reason to show we can.